1) Field of the Invention
The present invention relates to a technology to print an encrypted application document.
2) Description of the Related Art
An application such as Acrobat Reader® by Adobe® Systems Inc. has a function of encrypting document data by accepting document authentication information such as a document password to keep others from reading the document (see website of Adobe® Systems Inc., “with Adobe Acrobat, PDF can be used more effectively” (http://www.adobe.co.jp/acrofamily/features/acro_nikkei/page4.html)).
When printing such encrypted document data created by a personal computer (PC) on a printer connected to a network such as a local area network (LAN), an application decrypts the encrypted document based on a document password input, and sends the decrypted document to the printer driver. The printer driver then transmits the decrypted document to the printer on the network; and the printer prints the document directly.
To ensure that such encrypted document is not printed by others without permission, the printer driver prompts a user to input a job password for each print job upon receiving a request for decrypting and printing a document on the application. Then the printer driver transmits the document data and the job password to the printer. FIG. 17 is a schematic of a structure of print data used in the conventional printer driver and printer. A data for specifying a printer-job-language (PJL) job password is added to the head of a portable-document-format (PDF) document data (plain text).
The printer prompts the user to input an authentication password, and only when the authentication password input is valid, it starts printing the document.
However, in the conventional printer driver and printer, since a document encrypted by the application is decrypted at the time of printing, the document data is transmitted through the network in a plain text form from a PC to the printer. The plain text document data is subject to an interception by a malicious third party.
Even when the job password for each print job is employed to keep the malicious third party from printing out the encrypted document, the encrypted document can be intercepted by the third party on the network because the job password is in the plain text form. Furthermore, the decrypted document data is temporarily stored in a recording medium such as a hard disk drive (HDD) and a memory of the printer, and hence a user having a system administrator account can refer to the document data stored in the plain text form.
As described above, in the conventional printer driver and printer, the security problem occurs when a document data encrypted by an application is printed through the network.